Some types of electronic circuits use relatively little power, and produce little heat. Circuits of this type can usually be cooled satisfactorily through a passive approach, such as convection cooling. In contrast, there are other circuits which consume large amounts of power, and produce large amounts of heat. One example is the circuitry used in a phased array antenna system.
More specifically, a modern phased array antenna system can easily produce 25 to 30 kilowatts of heat, or even more. One known approach for cooling this circuitry is to incorporate a refrigeration unit into the antenna system. However, suitable refrigeration units are large, heavy, and consume many kilowatts of power in order to provide adequate cooling. For example, a typical refrigeration unit may weigh about 200 pounds, and may consume about 25 to 30 kilowatts of power in order to provide about 25 to 30 kilowatts of cooling. Although refrigeration units of this type have been generally adequate for their intended purposes, they have not been satisfactory in all respects.
In this regard, the size, weight and power consumption characteristics of these known refrigeration systems are all significantly larger than desirable for an apparatus such as a phased array antenna system. And given that there is an industry trend toward even greater power consumption and heat dissipation in phased array antenna systems, continued use of refrigeration-based cooling systems would involve refrigeration systems with even greater size, weight and power consumption, which is undesirable.
In addition, some phased array antenna systems include a number of modules, such as transmit-receive integrated microwave modules (TRIMMs) or “slats”, that include a row of antenna elements and corresponding circuitry. For example, a module may include a row of sixteen antenna elements. In some cases, several such modules are arranged adjacent each other so that the rows of antenna elements on abutting modules line up to form a continuous row of antenna elements, and so that other modules define other similar rows. The result is a two-dimensional array of antenna elements.
For some applications, it is desirable to minimize the size of the antenna elements on each module, and the size of the module. For example, as the operational frequency of the antenna progressively increases, the size of the antenna elements needs to progressively decrease, and the size of the module needs to progressively decrease. However, reductions in the size of the antenna elements and the size of the module may be limited by the size and location of the circuitry required for the module. Thus, in some cases, it may be desirable to use the complete width of the module, from one edge to the other, to accommodate particular circuitry, such as transmit-receive modules (TRMs). There are existing cooling systems that utilize edge areas outside of the circuitry present on a module, but this prevents use of the entire width of the module for circuitry.
A further consideration is that, where the coolant is a two-phase coolant, a separator is sometimes provided to separate coolant in a vapor state from coolant in a liquid state. The separator is physically separate from all of the modules, and takes up valuable physical space, thus causing the cooling system to be less compact than would otherwise be desirable.